例句與造句

1. These are doubly ruled surfaces of negative Gaussian curvature.
2. The hyperbolic paraboloid and the hyperboloid of one sheet are doubly ruled surfaces.
3. The hyperbolic paraboloid is a doubly ruled surface : it contains two families of mutually skew lines.
4. It's difficult to find doubly ruled surface in a sentence. 用doubly ruled surface造句挺難的